What's the scariest thing to ever happen to you health-wise?

I had a kidney stone that got stuck in my bladder and continued to grow. The scary part, I thought it was just a kidney stone and every time I started passing blood I thought "ok, this is it, a couple of days and this will be over". Then it would stop and I'd feel better for a couple of weeks. Maybe. Then I'd lift something heavy or move wrong and start passing blood again.
This went on for about a year with the bad days getting more and more frequent before I decided I would never pass it and needed to see a dr. By that time it had grown to the size of an egg and I wasn't having any good days.

they only keep getting scarier, but I was told I had cancer once. It scared me straight for 2 weeks. I quit smoking tobacco, drank more water and did a 14 day detox. told no one and 2 weeks later went back and it was gone. They tried to get me to start chemo on the spot.

When my gallbladder went out the pain was blinding.

Scariest would be when I coded after an asthma attack in front of my parents.

Chronic pneumonia as a child, close to death, but got a lung surgery to patch that mess up

I was cut into during surgery while I was wide awake without anesthesia.

Being hospitalized with two different near death experiences

Had my tonsils out when I was a kid.

Dying. I don't recommend it.